Field
The disclosed concept relates generally to electrical switches and, more particularly, to electrical switches such as, for example, dimmer switches. The disclosed concept also relates to mounting assemblies for dimmer switches.
Background Information
Electrical switches, such as dimmer switches, are commonly used to control the amount of power delivered to an electrical load, for example, in order to control the intensity of a lighting load, or to control the speed of a ceiling fan.
A dimmer switch is typically mounted to an electrical box disposed in a wall, and is electrically connected between a power source and the electrical load. The dimmer switch generally includes a faceplate coupled to the electrical box, and a user interface, such as a rotating knob, linear slider, or rocker switch, which is movably disposed on the faceplate. The dimmer switch may also include a button or toggle for switching the load ON and OFF. The user interface cooperates with a semiconductor switch, such as field effect transistor (FET), to control the current delivered to the load. That is, the rotating knob or linear slider user interface is movable (i.e., adjustable) to correspondingly to adjust (i.e., control) the current delivered to the load and thus the intensity of the light or the speed of the fan.
A conventional FET mounting assembly 2 is shown in FIG. 1. As shown, the mounting assembly 2 includes a FET 4 mounted to a grounded metal strap 6 (e.g., heat sink). Specifically, the FET 4 includes a metal tab 8 having a thru hole 10. An insulator 12, which also has a thru hole 14, is disposed between the metal tab 8 and heat sink 6 to electrically isolate the components. A screw 16 extends through an insulating bushing 18, which itself extends through hole 10 of metal tab 8, hole 14 of insulator 12, as well as a corresponding thru hole 20 in the metal strap 6, in order to fasten the FET 4 to the heat sink 6. In the example, shown, a washer 22 is disposed between the head of the screw 16 and the shoulder of the insulating bushing 18. Among other disadvantages, such FET mounting schemes are not as robust as desired and are prone to suffer from problematic issues, such as dielectric breakdown.
There is, therefore, room for improvement in dimmer switches and in mounting assemblies therefor.